Why did Luke have a full sized droid dipping goop chamber in his room? I mean they couldn't have used it that often, and it looks very expensive.

Why did Luke have a huge apparatus for fully submerging doids in goop in his BEDROOM?

His aunt and uncle run a small vaperator farm, with one humanoid droid and one little sausage droid. That they JUST bought. The Jawas have a droid goop sumberging chamber in their sand crawler, you can check the floor plans. And they come by once every lunar cycle or so. More than often enough to dunk a droid in some goop for a bit and then raise them up and have it all drip off for the cameras.

It just doesn't make any sense to invest in this kind of apparatus to have at home. Maybe that's why his aunt and uncle were portrayed as unhappy and struggling, barely able to afford to replace vaperator coils which are the life blood of their farm (along with the solar panels).